1. Field of the Invention
The invention is generally related to the area of optical communications. In particular, the invention is related to a pluggable platform in small form factor to accommodate passive optical devices to retrofit into an existing system, where the pluggable platform in small form factor is provided with an interface for tractability and controllability of the passive optical devices.
2. The Background of Related Art
To meet the ever-increasing demands for high bandwidth and more flexibility in modern communication networks, utilizing optical fiber networks capable of transmitting multiplexed channel signals are becoming increasingly popular. Many optical devices have been designed to meet the demands. Among the optical devices, pluggable optical units are key elements in many applications of optical fiber communications. A cost-effective and reliable optical pluggable unit having low insertion loss and versatile function with flexibility is often required. FIG. 1 duplicates FIG. 1 of U.S. Pat. No. D467,544 to show a small form-factor pluggable optical transceiver module.
In terms of functionality, most of small form factor pluggable optical modules are active devices (e.g., transceivers) with high speed electrical interface. They increase the flexibility of a network and are being widely deployed in networks. Usually they are mounted on a 19-inch rack mount as shown in FIG. 2.
As in the real system, not only transceivers but also many other passive components (optical attenuator, isolator, filter, etc.) are required. These passive devices used to be installed in fixed positions inside an enclosure. Once they are deployed, they are difficult to be traced in an enclosure because they have no electronic interfaces linked with a system, thus very inflexible. On the other hand, there are many slots in a 19-inch rack mount, these slots are often not fully occupied. They may be the perfect positions for the many passive devices. FIG. 3 shows a typical application diagram with 10 transceiver slots, slots number 4 to 8 and 10 are not used. After the system is already installed, some optical transceivers need a filter at the receiving port or an isolator (or attenuator) at the transmitter port, hence one or more passive devices may be deployed to occupy the slots 5 and 7 without touching the inside of other chassis on the rack mount.
Ideally, such passive devices shall be coming in a pluggable platform or in a chassis retrofitting or pluggable to an existing system. Pluggable devices are widely available in electronic forms these days. A device that belongs to the pluggable category typically needs to be turned on and functioning as soon as it is inserted into an existing system or device. When it is unplugged from such a receptacle, neither the system that hosts the pluggable device nor the pluggable device itself would be damaged. Pluggable devices may be added or removed from a system without interrupting the synchronization between the devices and the system. Therefore, it is not required to have a power reset when replacing or upgrading such devices. Pluggable devices add on a good deal of system application upgrade flexibilities and are becoming more and more popular for electronics.
This invention disclosure intends to introduce a stand-alone pluggable device to host passive components. In one embodiment, the device is designed as a form factor of optical transceiver, including optical interconnection, interface electronics and housing case. The interface electronics shall be simplified because no high speed circuit is needed. In one embodiment, there may be a simple EEPROM integrated circuit for electronic tag function (storing some device information), and an on-line pin indicating the presence of the device to a system.